Re: Solaris ZFS on Linux [Was: Re: the " 'official' point of view"expressed by kernelnewbies.org regarding reiser4 inclusion]

David Masover
2006-08-02T03:52:09Z

Ian Stirling wrote:
> David Masover wrote:
>> David Lang wrote:
>>
>>> On Mon, 31 Jul 2006, David Masover wrote:
>>>
>>>> Oh, I'm curious -- do hard drives ever carry enough
>>>> battery/capacitance to cover their caches? It doesn't seem like it
>>>> would be that hard/expensive, and if it is done that way, then I
>>>> think it's valid to leave them on. You could just say that other
>>>> filesystems aren't taking as much advantage of newer drive features
>>>> as Reiser :P
>>>
>>>
>>> there are no drives that have the ability to flush their cache after
>>> they loose power.
>>
>>
>> Aha, so back to the usual argument: UPS! It takes a fraction of a
>> second to flush that cache.
>
> You probably don't actually want to flush the cache - but to write
> to a journal.
> 16M of cache - split into 32000 writes to single sectors spread over
> the disk could well take several minutes to write. Slapping it onto
> a journal would take well under .2 seconds.
> That's a non-trivial amount of storage though - 3J or so, 40mF@12V -
> a moderately large/expensive capacitor.

Before we get ahead of ourselves, remember: ~$200 buys you a huge
amount of battery storage. We're talking several minutes for several
boxes, at the very least -- more like 10 minutes.

But yes, a journal or a software suspend.